1. Field of the Invention
This invention is concerned with novel builder materials and detergent compositions containing builder materials which provide good heavy-duty detergency in combination with conventional detergent actives.
The function of a "builder" in detergent compositions has not been in the past clearly defined except in terms of the enhancement of detergent activity of soaps and detergents when builders are employed in combination. It, however, is known that the presence of builders particularly enhances detergency when the detergent compositions are employed in hard water, so it has been conjectured that some large amount of the effectiveness of the builder results from the ability to tie up the so-called "hardness ions" in the water, i.e., calcium and magnesium ions. Builders have been therefore regularly employed in washing compositions designed for use in heavy-duty applications-- that is, cleansing of washable fabrics, particularly cotton, in powered washing machines.
Increased concern over water pollution has caused a great demand for substitutes for the components of conventional heavy-duty detergent compositions. Thus branched-chain alkylbenzene sulfonates, which were used for many years as the active components of most heavy-duty detergent compositions, have been replaced in the United States as well as many foreign countries with linear alkylbenzene sulfonates, which possess the advantage of being biodegradable and thus do not contribute to the foam situation which had begun to become serious in rivers, streams and lakes.
A more recent, and one believed by many to be a more significant problem, lies in the phenomenon of eutrophication, which has contributed to the destruction of water bodies. This phenomenon, which involves the greatly increased growth of algae in the water bodies, results in removal of dissolved oxygen from the water bodies resulting in eventual death of almost all present living organisms. It is believed by many, and increasing evidence appears to indicate, that the presence of phosphates, largely derived from heavy-duty detergents, accounts for eutrophication.
Attempts to eliminate the phosphate builders have been made using one of two approaches. First, efforts have been made to provide new detergent-active materials which do not require the presence of any builder for heavy-duty washing, and secondly, efforts have been made to simply replace the phosphate builders with builder materials which lack the nutrient potential of phosphate. The second approach has resulted in the introduction of various materials as builders none of which has been completely successful in replacing phosphates because of other problems encountered. For example, the salts of nitrogen-containing polycarboxylic acids have been proposed, the most widely used-- the polysodium salt of nitrilotriacetic acid--encountering extreme difficulty from findings that this compound, when in the presence of certain heavy metals, possesses possibly dangerous teratogenic activity. Other materials, such as various metal carbonates and silicates, etc., have been used but have been found to leave substantial deposits on clothes and in many cases are dangerously corrosive to human skin. Polyelectrolyte builders such as copolymers of ethylene and maleic acid are beleieved to be incapable of bacterial degradation and thus possess some disadvantages in use. Sodium citrate is used in some heavy-duty liquid detergents, its usefulness being limited from economic considerations.